The Secondary Four pupil will be remanded for psychiatric assessment and be charged on Tuesday with murder, police said.

The victim, a 13-year-old Secondary One pupil, was found with multiple stab wounds in the school’s toilet at about 11:40am, according to The Straits Times newspaper. He was pronounced dead at the scene by a paramedic.

Police said the two students did not know each other, according to preliminary investigations.

A lockdown of the school was reportedly put in place this morning and teachers and pupils were ordered to remain in their classrooms. They were released only after 3pm, a media report said.

A parent, Jacky Huang, 43, said he rushed to the school after receiving a message from his daughter that there was someone wielding an axe in the school.

He showed text messages and a video sent by his daughter showing schoolchildren running from the crime scene.

River Valley High School, in the Boon Lay area in Jurong West, is a secondary school with pupils aged 12 to 18 who sit for the A-level examinations.